Means for forming a well bore



June l 1926.

J. A. ZUBLIN MEANS FOR FORMING A WELL BORE Filed NOV. 14. 1922 A i., .lune Il, D sr i A T' i JOHN A. ZUBLIN, LOS'ANGELES, GALIFORISI'IA;I

MEANS FOR FORMING A WELL BORE.

Application led November 14, 1922. i Serial No. 600,840. ,l

l@ forming, byrotary means, a bore extending beyond the lower end of a well casing and having a diameter greater than the internal diameter of the casing.

Another object is to provide a rotary nonw collapsible .underreaming drill.

A further object is to provide a rotary underreaming drill having no moving parts and which is eccentrically disposed on the drill stem, whereby the drill may be lowered a@ into the Well bore with its axial center out of registry with the axis of the bore, tlie drill functioning ``upon rotation to automatically center itself and the drilllstem in the bore and subsequently form an enlarged continuation of the bore.

Various other objects and advantages will be more fully apparent from the following description of the accompanying drawings which form a part of this disclosure, and

`^` which illustrate preferred forms of embodiment of the invenion.

f the drawings:

Figure 1 is a vertical section through the lower portion of a well boreshowing a cemented casing and illustrating the method of lowering or raising the -non-collapsible underreaming drill through the bore.

Figure 2 is a similar section showing another formiof the drill in position for forming an underreamed bore.

Figure 3 is an elevation of the drill looking at its left hand edge, as viewed in Figures 1 and 2.

lFigure 4 is a plan section of the drill on line 4 4 of Figure 2.

In Figures 1 to 4^ there is illustrated a one piece drill of more or less general fishtail type and in this instance comprises a` shank 1 having a screw-threaded tapered pin 2 adapting the drill for attachment to a tubular drill stem or collar 3 and terminatin with a diametrical pilot blade or Kish-tail lade 4 of fish-tail formation axially ali ed with the shank. 'Projectin laterally om one edge of the fish-tail b ade in alignment therewith 'is an offset underream- `shown in Figure 1.

ing blade 5 extending beyond the pilot blade, whereby the blade .5 has a permanently maintained underreaming radius greater than the boring 'radius of the pilot blade. y The cutting edges of the pilot blade are turned in opposite directions in the usual manner to produce a more or less shearing cut, and the blade 5 has its lower end dressed to a cutting edge 6 extending backwardly and inwardly from a lead point 7 which extends in the direction of rotation.

The shankv 1 has Huid passages 8 and as shown in Figure 1 these passages may discharge at the upper portion of the drill, with the sides of the drill provided With depressions or flutes 9 directing the fluid downwardlytowards the cutting end of the pilot blade, or as shown in Figures 2 to 4 may .continue downwardly past the underreaming blade 5. It will also be evident that, if thought necessary or desirable, the fluid passage on one side of the drill may be extended past' the underreaming blade as shownin Figure 2 and the Huid passage on the other side of the blade may terminate at the upper portion of the drill as One -manner in which the extended fluid passages, shown-in Figures 2 to 4, may be formed is to form a groove in the face of the drill and then weld over the groove, a longitudinal-half section of pipe 10.

The upper ends of the fluid passages 8 communicate with the interior of the hollow drill 'stem through which the circu-k lating fluid is forced during drilling.

In Figures land 2, the well casing 11 is shown cemented in the well bore and the bore has been extended a short distance beyond the lower end of the casing in the usual manner.

In the herein proposed method of forming v an underreamed bore beyond the lower end of the casing, the drill having been attached to vthe lower end of the string of drill tubing, is lowered through the casing, with its axis, which is indicated bythe oken line 12,. to one side of or out of registry with the axis 13 of the casing.

In this manner it is possible to lower through the casinga non-collapsiblel under-`| By subsequently rotating' the drill there will be created a natural tendency Jfor the drill to automatically center itseltl in axial alignment with the axis of the casing and to automatically eiiect an enlargement of the bore.

l'Vhen so centered the pilot blade 4 will bore a pilot hole in advance of the underreaming blade 5, the blade 5 functioning to ream said pilot bore to a diameter larger than that of the casing (see Figure 2). One particular advantage of the pilot blade resides in the fact that it serves to positively guide the'drill, in the same manner as a bearing at the end of a shaft, and thereby prevents side thrusts to which the reaming blade may be subjected, from causing a transverse deflection ot' the drill. As shown clearly in Fig. 3 and in Fig. 4 the underreaming lblade 5 is formed integrally with the pilot blade or fish-tail blade 4 and eX- tends laterally therefrom in the same plane and in alignment therewith. It is very desirable to have the underreaming blade 5 in the same plane as the fish-tail blade 4 because of the economy of production, the blades 4 and 5 being easy to form and requiring but a minimuml of material. An-

' other reason is that the pilot blade and the ishtail blade both cut in the same radial plane. Therefore, the force against the pilot blade is opposed and counteracted by the 'force of cutting of the fish-tail blade. If the pilot blade Were placed in a different plane from the {ish-tail blade 4, the force of cutting would tend to drive the Whole bit laterally, since there would be no direct opposition to the cutting force, and the result would probably be the drilling of a crooked hole.

I claim:

In 'a one-piece bit of the class described, the combination oli: a shank having means whereby said bit may be secured to a drill column; a diametrical iish-tail blade integral with and depending from said shank, the lower end of said {ish-tail blade being prepared for cutting; and an offset underreaming blade formed integrally with said fish-tail blade and extending laterally from one edge of said fish-tail blade and in alignment therewith so as to cut in the 'same diametrical plane as said iSh-tail blade.

Signed at Los Angeles, California this 6th day of November 1922.

' JOHN A. ZUBLIN. 

